1. Field of the Invention
The invention relates to a polymer electrolyte, to a half cell, and to uses of the half cell and of the polymer electrolyte.
2. Prior Art
Numerous half cells for electrochemical measurements, such as potentiometric or amperometric measurements, are known. In particular, such half cells can be embodied as reference electrodes, which are used in combination with potentiometric or amperometric sensors. In such reference electrodes, it is important that they output as constant a reference potential as possible.
In one type of reference electrodes, there is a fluid reference electrolyte, such as an aqueous potassium chloride solution, which can be brought into contact with a fluid measuring medium via a liquid connection (also known as a “liquid junction”). To avoid or reduce an unwanted mass transfer between the measuring medium and the reference electrolyte, the liquid junction is typically designed as a more or less porous diaphragm. One disadvantage of such liquid junctions, however, is that soiling or even plugging up of the pores can occur, which can lead to considerable faulty potentials and possibly interruptions.
In another type of reference electrodes, instead of the diaphragm, a single opening or a plurality of openings is provided, as a result of which the aforementioned problem of soiling can be largely avoided. However, this embodiment means that instead of the otherwise usual fluid or gel-like reference electrolyte, a non-flowable reference electrolyte is used, to prevent the reference electrolyte from flowing out. A polymer electrolyte in the form of a hydrogel, which for instance contains a saturated aqueous potassium chloride solution and preferably additionally suspended potassium chloride is especially well suited for this purpose.
In European Patent Disclosure EP 1124132 A1, which is hereby incorporated by reference in its entirety, a reference electrode of this generic type is described which contains a polymer electrolyte that contains a polymer on the basis of monomers selected from N-substituted acrylamides and/or methacrylates. For instance, the methacrylate is a methacrylate with at least two hydroxy groups, and in particular 2,3-dihydroxypropyl methacrylate.